(1) Field of the Invention
The present invention relates to a solid-state imaging device, a camera and so on which uses the solid-state imaging device, and in particular to a color filter included in the solid-state imaging device.
(2) Description of the Related Art
In recent years, the range of application for solid-state imaging devices such as digital still cameras, digital video cameras and cellular phones has been expanding rapidly and coloration technology has become essential technology in any field.
FIG. 1 is a diagram which shows part of a cross section structure (more specifically, three unit pixels) of a conventional solid-state imaging device 6. As shown in FIG. 1, the pixel portion of the solid-state imaging device 6 has a structure in which a P-type semiconductor layer 602, an inter-layer insulation film 604, a color filter 606 with a multi-layer film structure and a micro-lens 607 are laminated sequentially on an N-type semiconductor layer 601. Note that a photodiode 603 is formed on a side of the inter-layer insulation film 604 in the P-type semiconductor layer 602, and a light shielding film 605 is formed on the inter-layer insulation film 604.
Incident light on the solid-state image device 6 is collected by the micro-lens 607 and, after being separated into specific colors by the color filter 606, enters the photodiode 603 (see for example, Patent Document “International Pamphlet Publication No. 05/069376”).
Color separation is realized using the color filter, and a page of image data can be generated by accumulating the above photoelectrically converted signal in all of the unit pixels (see for example, patent documents “Japanese Patent Publication No. 7-311310”, “Japanese Patent Publication No. 2000-180621” or “International Pamphlet Publication No. 05-069376”).
In order to protect pixel units and circuit units, normally a tri-silicon tetra-nitride film is formed as a barrier film (known as a “protection film”) in the solid-state imaging device. Subsequently for example by composing the color filter in the solid-state imaging device by layering a silicon oxide nitride film and a tri-silicon tetra-nitride film, incident light reflection can be controlled (see for example, Patent Document “Japanese Patent Publication No. “2000-252451”).
Conventionally, improvement in image quality has always been in demand, and increases in the amount of pixels and color reproducibility are also in demand.
However, there is the problem that an adequate color reproducibility cannot be obtained by the conventional solid-state imaging device 6. The problem is explained below by making use of the drawings.
FIG. 5C is a diagram which shows a conceptual structure of the color filter 606 included in the conventional solid-state imaging device 6. Additionally, FIG. 5D is a diagram which shows the color separation characteristic of the color filter 606.
In the conventional color filter 606 shown in FIG. 5C, the transmission band for blue (a property curve 424) is narrow and the color reproducibility is poor in the same way as the color separation characteristic is shown in FIG. 5D. In other words, there is the problem that although the structure of the conventional color filter 606 can be thinned, an adequate color reproducibility cannot be obtained.
Further, sometimes when a multi-layer film interference filter which includes a protection filter (see for example Patent Document “International Pamphlet Publication No. 05-069376”) is used as the color filter (generally, the color filter is formed using laminated film of low refractive index material and high refractive index materials, however a protection film such as a barrier film is formed outside the color filter), the protection film produces adverse effects for the color filter (see for example Patent Document “International Pamphlet Publication No. 05-069376”).
In addition, when a set wavelength of the color filter is not appropriate for the film thickness of the barrier film, “interference” is generated and the color separation characteristic (also known as the transmission spectra) for the incident light is affected. In addition, there is a large effect on the position and color separation characteristic of the barrier film.
Further, when a planarizing layer and so on is formed using Chemical Mechanical Polishing (CMP), there is the problem that the color separation characteristic will vary due to the increase in film thickness variation.